Plastic containers, such as a bottles for consumer beverages, are most commonly produced using an Injection Stretch Blow molding process. The process begins with the molding of a container preform (preform) using a molding process such as injection or compression molding. As need be, the preform is then transferred to a conditioning station for heating of parts thereof to be reshaped such that they become malleable and thus amenable to reshaping. Next, the preform is transferred into a blow mold for reshaping into the finished container. Blow molding typically involves the substantially simultaneously steps of axial and radial stretching of a body and base portion of the preform within a blow mold. Axial stretching of the preform is provided with extension of a stretch rod—mechanical stretching. Radial stretching of the preform is provided with pneumatic inflation with blowing of compressed air into the interior of the preform.
With reference to FIG. 1 below, a typical prior art preform 1 is depicted. The preform 1 comprises a generally tubular body 11 having a neck finish 10 and a base 12 at an open end and a closed end thereof respectively. The neck finish 10 forms part of the finished container and is configured to receive a closure (not shown) for capping thereof. A typical neck finish 10 includes one or more helical threads for coupling with complementary threads on the closure. The neck finish 10 also typically includes several outwardly depending rings that cooperate with anti-tamper features on the closure (i.e. pilfer ring) and for assisting in the handling and blow molding of the preform (i.e. support ledge/ring). The body 11 and base 12 of the preform 1 are the parts thereof that are reshaped in the stretch blow molding process to form the body of the container. The base 1 of the preform is typically hemispherical in shape forming a domed end. That is, the base has a hemispherical dome shape that is characterized by a generally spherical inside surface and outside surface each having a constant radius. A bottom wall thickness BWT of the base is fairly constant. The base also includes a small axially protruding gate vestige 13 that extends from a distal tip of the spherical base. The gate vestige 13 is a manufacturing artifact of the injection molding process by which the preform has been produced. The gate vestige is formed in the gate/sprue of the mold through which the molding material is injected into the molding cavity. Typically, the gate vestige is a short and narrow cylindrical feature that blends, along a small annular blending radius, onto an outside surface of the base 12.